This invention relates to a mold equipment suited for mass production of plastic moldings by means of metal molds.
Most of soft and semihard polyurethane foams, which are generally used in such fields as cushions for vehicles and household furnishings, are manufactured on hot or semi-hot molding equipment.
In one such molding equipment for plastics, a mold transfer conveyor is horizontally disposed in an endless manner at a certain height above a floor so that a metal mold may be circulated at a speed of approximately 5 m/min through several manufacturing processes including pouring, heat curing, cooling, and mold releasing.
With such system using the horizontally circulating conveyor, however, it is very difficult to achieve reduction in energy and labor because of an increase in equipment size and extended manufacturing line (usually more than 100 m).
For example, a hot curing process uses a temperature ranging from 200.degree. C. to 300.degree. C., so that a cooling process subsequent thereto requires a long cooling zone for cooling by means of cooling air or a shower.
Moreover, since a hot blast is generally used for the heat source of a heating oven, the inlet and outlet of the oven must be opened and closed with every passage of the mold therethrough, resulting in a reduced thermal efficiency and increased consumption of heavy oil.
Further, the conveyor continuously extends over the whole length of the manufacturing line, so that it is impossible to adjust the processing time for each process. Thus, constant-speed performance of all processes will necessarily require many operators (usually ten or more operators) for constant attendance for each process.
The inventors hereof have previously proposed as an improvement to counter the aforesaid circumstances a mold equipment (disclosed in Japanese Patent Application No. 104661/78 corresponding to Japanese Patent Disclosure (Kokai) 30959/80, laid-open for public inspection on March 5, 1980) capable of reducing the length of the manufacturing line and the overall equipment size, thereby achieving reduction in labor, energy and equipment cost.
According to the invention described in Japanese Patent Application No. 104661/78, however, metal molds poured with foamable material are continuously arranged over the whole length of a cooling water tank, and one among the row of molds at the tail end thereof is forced out by a push-in cylinder in the conveyance of the molds from the outlet of the water tank into a first lift chamber moving up and down between the water tank and a heating oven for the next process. Also, in carrying the metal molds from the outlet of the oven into a second lift chamber moving up and down between the oven and a water tank for the next process, the tail ender among a row of molds arranged over the whole length of the oven is forced out into the lift chamber. Accordingly, the metal molds in the water tank and oven must be stopped while other molds are moving up and down in the first and second lift chambers. Thus, it would be impossible to fully reduce the time for the circulation of each mold through the mold equipment.
The object of this invention is to provide a mold equipment capable of full reduction in the circulation time of a metal mold and hence in the overall size of the equipment.